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Was hoping someone could enlighten me to the best of their knowledge about filter cabinet on the infinity MVB furnace.

I have the option to go w/about 3-4 different type cabinets of filter types... 1", 4" 5" my wife was always buying those 12.00 3m filter before with old furnace. Anyway, I want to make a good decision as to what type of cabinet or if it's better just to stick with the return drop (THAT IS CURVED INWARDS AT BOTTOM) - I believe if they put the cabinet or box they plan on not curving the return drop into the furnace... but just dropping to the floor and affixing the filter cabinet. The marketing of the brochures is sure fancy but sometimes it's all about the marketing, not even sure if I can buy these types of filters at home depot?

I was told the MVB080 comes with a carrier filter cabinet so I might as well. I want to make sure that the filters are reeadily available for the size cabinet also if the thickness makes a difference... They had honeywell F100/F200 and a few others to offer, basically they said it's up to me.

Second thing is the chimney liner, the old 80% furnace has 5" B- vent running up through the house and about 15-20 once in the attic and out roof, total B vent run is about 30' The water heater is a 40,000 btu has a 3" vent coming out now and is T'd into the furnace exhaust (which is coming out)

Do I need to put a chimney liner in with the water heater by itself? We have some frigid days in Chicago. I have read that it's necessary, the sales guy thought the same but after seeing it decided it would probably be ok leaving it with the 5" B- vent. It does have (2) 45 deg bends in the attic before going out roof. He said it's expensive to replace if they did.

Honestly, w/the co I don't care but want to do what is right. Can't they push this down from the chimney on the roof and llet it snake though the 5" B-vent?

filters and venting

your filter cabinet should present no problems with the availability of filters on the market. I personally like the 3M filters. Another option you can discuss with your contractor is the advantages of an Electronic Air Cleaner (EAC). You can utilize your existing drop and it would probably pay for itself in 3 years or less compared to the cost of the 3M filters. The EAC also surpasses the 3M in efficiency.

lining a class B vent? No can do. Check with your local code enforcement office about the venting requirements of your water heater. Beings you have a 30 foot vertical rise of 5 inch, I would think that might pass, but let the agency be your guiding light.

filters and liner

RE2, are you saying that the MVB080 cabinet (I was told that comes with the furnace)... will allow for different type filters (including the 3m) and not just carrier models? I was under the impression that this was like a 4" thick filter cabinet, do I want 4" or 1" thick? They are going to change the drop and increase the return main in the area above the furnace (from 8x14 to 8x20) to make sure the return cfm is ideal... Wouldn't the drop opening need to match the depth towards the furnace ie; 1", 4" or 5" (plus the opening size) of the selected type filter cabinet?

Hot water heater venting - wouldn't B vent be ok to line since it's already a double wall pipe? I will try to find out about the code, not sure if the contractor will need permits to do the hvac work... Isn't there an Industry standard that you guys use?
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Dash, you help allot of people on this forum and have already taught me a few things with your posts. Our present old furnace was short cycling or tripping ut on hi limit w/the 3m filters (1" thick) atthis time we have a 60 cent filter in there and it doesn't Truip out as fast. I can't wait until the infinity system is finished.

Why am I so interested in the engineering aspect of this job? Let me explain.

When I built my house in 1992 I did all the electric myself, floors and some trim stuff but knew little about the plumbing and hvac so left that for the professionals, well it turns out the return is way undersized and the furnace way oversized. Now with my heat exchanger completely rusted out because of years of short cycling, my negligence of know-how allowed a inadaquete ducting system to be installed right in front of my face, I should have known when we moved in - the duct work sounded like a thunderstorm! The kid installers came buy many times with his sheet metal "stiffners" to stop this oil canning. Boy was I stupid. I wish I knew then what I know now. Anyway, it was a terrible job with leaky ductwork. The only thing I knew back then was hi/low return grills so I paid extra for them : ((

I have my own ductilator and it's pretty neat to understand the cfm in and out, from the plenum to the main suppply/return runs, takeoff branch runs and the grill openings.

It's gonna be right this time. I want to know exactly what's going to be installed, (hopefully in about two weeks) I got two bids and am waiting for the third - (these two bids do not include the sears proposal I received)

The qulaity of the work, experieince and Better work is more important to me than the price, it's sometimes difficult because the sales people are not always installers, my goal is an honest and conciencous install.

OK, now that that's over.... what is esp of the duct system? Are you suggesting the cheapy filter as a temperary only? I'm guessing that you're thinking that airflow should be measured and the filter should be sized after air flow is measured...? Let me ask this, how can I put a cheapy 1" filter in a cabinet sized for a 5"? Do I not need to make the decision as to what cabinet before this is all connected and fitted at the return?

Oh, almost forgot, one contractor says bring the return drop flat to the floor (L or 90 deg in) the other will put a curve in the bottom just before the filter. He even said that he would screw a few home made turning vanes in the curve of the drop so air will pass through the filter evenly - said it would help distribute air across rather than just on the bottom? That guy suggested a 5" honeywell F100/F200 cabinet and some more elaboarte options as well. The electronic sounds good but the snapping will scare my cat, he is very stubborn and is a pansy for lack of a better word. His littler box is in my mechanical room, want to keep it that way.

The energy consumption of the 3m or restrictive filter is good to know think I'll throw an amp probe across the circuit when this is said and done.

Ask your contractor(s) if adding a media filter may require larger ducts,if the flatly say no,keep looking or talk to the owner to see if he agrees,then keep looking.

In your case knowing you had problems,they should do a Manual J ,S and D,to size the system and cfms per room,select the equipment,and redesign the ducts.

Your ductolator is meant to be used after completing the Man. D,and determining the FR(friction Rate) to use with the ductolator to select the correct size.Without knowing the FR,using a ductolator is just a guess.

So in this example ,if the system was deigned at .08 FR,with a standard filter,and you added the media ,most or all ducts would be to small.

You only have so much ESP available from the fan,nfrs, tell you how much and it varies .PD from coils,grilles,filters ,etc., take away some,Whats left over gets divided by the TEL,longer TEL the lower the FR will be,and the duct will need to be larger.

Usually we can increase return sizes or add additional ones to compensate for adding a media filter.They should design yours correctly from the start.

venting

If you are venting up a chimney, it should have a liner sized as a common vent. Only a few B-vent mfrs. allow their vent used inside a chimney as a "liner". If the B-vent is run separately leaving just a 40MBH WH, you would definitely need a liner for the orphanned WH. Better to common vent in most applications.

When your B-vent goes all the way through the roof you are fine. For natural draft appliances the code limits only max no min. Over time, your large B-Vent will rust out, but it is well possible, that by then, you would install a high efficiency water heater.

Wider the filter, more filter surface, less pressure drop. Go with 5” filter. Electronic filters only work better than high MERV pleaded filters when kept very clean and I still have to find the customer who takes care enough.

hearthman,
what mfg is able to go thru the 5" b vent, need a new cap as well correct? Also what is common vent - you talking w/the 80% efficient model furnaces?

tostaos,
you said when your B-vent goes all the way through the roof you are fine. For natural draft appliances the code limits only max no min, does that mean 5" b vent with 3" flex inside It'll be fine? Will the B vent rust out as fast even if it's aluminum lined now (not sure installed in '92) w/ the 3" flex liner...

That is a great link, tells much about gas venting... although looked thru the 65 pgs and said nothing about lining B-vent.
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re2ell,
filter link shows up page not found? The filter is still negotiable because it's not installed yet, was wanting to know WHAT FILTER CABINET is best, and of course the filter but the case is the key, wanted an ideal filter that is not mfg specific (ad in only a carrier filter) The furnace is an MVB080 and the drop is like 24" OR 25"X10"
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tin nocker can you email me litegide24@yahoo.com not sure about that temp rise, would like to know and hopefully expert will do it right but said nothing about temp rise. Is that temp rise before or after the ductwork mods are done?

You don’t need a liner in a b-vent, it’s double wall and that’s all the code requires. There is no code that would not allow lining a b-vent and making a triple wall vent out of it. Normally you add a liner in a masonry chimney to make a double wall chimney out of it.

Originally posted by tostaos You don’t need a liner in a b-vent, it’s double wall and that’s all the code requires. There is no code that would not allow lining a b-vent and making a triple wall vent out of it. Normally you add a liner in a masonry chimney to make a double wall chimney out of it.

so does that mean that if i slid a new 4" bvent inside his 5" bvent i would have a quintuple wall vent!!!